Extension across the Laptev Sea continental rifts constrained by gravity modeling (original) (raw)
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Structure and geology of the continental shelf of the Laptev Sea, Eastern Russian Arctic
Tectonophysics, 1998
The Laptev Sea is of great significance for studying the processes of the initial breakup of continents. It is the southern termination of the Gakkel spreading ridge and thus the location of structural features resulting from a continental margin=spreading ridge intersection. The present-day understanding of the Laptev Shelf geology is based on the Russian multichannel seismic reflection data and extrapolation of the terrestrial geology. Geologic and plate-kinematic data are used to constrain the interpretation of the seismic reflection data. The Laptev Rift System consists of several deep subsided rifts and high standing blocks of the basement. From west to east these are: the West Laptev and South Laptev rift basins, Ust' Lena Rift, East Laptev and Stolbovoi horsts, Bel'kov-Svyatoi Nos and Anisin rifts. The central and eastern parts of the shelf have the greatest contrasts in the gravity field ranging from 60 mGal over the rifts to 50 mGal over the horsts. The rifts contain up to five seismic stratigraphic units bounded by clear regional reflectors and underlain by folded heterogeneous basement. They are suggested to be Late Cretaceous to Holocene in age and reflect different stages of spreading ridge=continental margin interaction. The estimated total thickness of the rift-related sediments varies between 4 and 8-10 km while the sedimentary cover on the uplifts is significantly reduced and generally does not exceed 1-2 km. An eastward decrease of the total thickness of the sedimentary sections from about 10 km in the South Laptev Basin to 4-5 km in the Bel'kov-Svyatoi Nos Rift and the simplicity of the entire rift structure may indicate a rejuvenation of the rifts in the same direction. The entire rift system is covered by the uppermost seismic unit, which probably reflects a deceleration of the rifting during the last reorganization of the North American=Eurasian plate interaction since about 2 Ma.
Petroleum Geoscience
The Laptev Shelf in the eastern Siberian Arctic represents a rare tectonic setting 12 where an active oceanic spreading centre, the Gakkel Ridge, intersects a continental margin. 13 The North America-Eurasia plate boundary follows the Gakkel Ridge and passes into a 14 continental shelf; this has resulted in the development of a wide rift system that has been 15 active since the Late Cretaceous. The new long-offset seismic profiles provide a reliable basis 16 for deciphering the structural characteristics of this rift system. We use two new seismic 17 profiles, along with one acquired in the 1990s, to examine the crustal architecture of the rift 18 system. Our approach combines seismic interpretation, time to depth conversion of seismic 19 profiles and 2D gravity forward modelling. The obtained results indicate the presence of 20 hyperextended continental crust beneath the Ust' Lena Rift Basin and exhumed continental 21 mantle at the base of the syn-rift succession along the rift axis. The upper crust was removed 22 by brittle stretching, while the lower crust experienced extreme ductile thinning. Our results 23 show that continental crust can be eliminated in the course of rifting without a considerable 24 heat input from asthenospheric mantle.
Tectonic of the Laptev Sea Region in North-Eastern Siberia
2000
Summary: Seismic reconnaissance lines were surveyed on the wide, virtually unexplored shelf of the Laptev Sea between the New Siberian Islands and the Taimyr Peninsula. The most pro minent ritt basin is the Ust' Lena rift with a minimum width of 300 km E-W at latitude 75 "N. It is bounded to the Laptev horst in the east by a westerly dipping major listric fault, the MV Lazarev fault. The 100 to 150 km wide Laptev horst is subdivided into three parts by minor rift basins. Another rift graben, the Anisin basin, is separated from the Kotel'nyi horst by a deep fault, the IB Kapitan Dranitsin fault. The onset of the rift is inferred to have been in the Late Cretaceous and the main extension took place from the Paleocene to the Oligocene.
Extension across the Laptev Sea continental rifts constrained by gravity modelling
Tectonics, 2015
8 The Laptev Shelf is the area where the Gakkel Ridge, an active oceanic spreading axis, approaches a 9 continental edge, causing a specific structural style dominated by extensive rift structures. From the 10 latest Cretaceous to the Pliocene, extension exerted on the Laptev Shelf created there several deep 11 subsided rifts and high-standing basement blocks. To understand syn-rift basin geometries and 12 sediment supply relationships across the Laptev Shelf, accurate extension estimates are essential. 13 Therefore, we used 2D gravity modelling and 3D gravity inversion to constrain the amount of crustal 14 stretching across the North America -Eurasia plate boundary in the Laptev Shelf. The latest 15 Cretaceous-Cenozoic extension in that area is partitioned among two rift zones, the Laptev Rift 16 System and the New Siberian Rift. These rifts were both overprinted on the Eurasian margin that had 17 been stretched by 190-250 km before the Late Cretaceous. While the Laptev Rift System, connected 18 to the Gakkel Ridge, reveals increasing extension towards the shelf edge (190-380 km), the New 19 Siberian Rift is characterised by approximately uniform stretching along strike (110-125 km). The 20 architecture of the Laptev Rift System shows that the finite extension of about 500 km is sufficient to 21 entirely eliminate crystalline continental crust. In the most stretched rift segment, continental 22 mantle is exhumed at the base of the late Mesozoic basement. The example of the Laptev Rift 23
Structure of the Laptev Sea Shelf–Eurasian Basin Transition Zone (Arctic Ocean)
Geotectonics, 2018
Based on obtained data, the paper considers the structure of the sedimentary cover and basement in the continent-ocean transition zone. We analyze the structure of modern tectonic activity zones in the Laptev Sea and structurally similar zones in the Novosibirsk Trough and the De Long Massif. Three sedimentary Anisin-Laptev, Amundsen, and West Laptev basins separated by basement uplifts are distinguished in sedimentary cover. The Anisin-Laptev Basin is separated from the West Laptev Basin by the North Laptev Horst and from the Amundsen Basin by an uplift stretching from the Lomonosov Ridge and covered by the Neogene-Quaternary deposits. The modern tectonic activity zone, marked by a rift valley and earthquakes, stretches across the continental slope from the Gakkel Ridge above a sedimentary rock sequence possessing many-kilometers thickness. The zone reached its present-day position in the Pliocene. Near the shelf boundary, the zone bifurcates, with one branch departing into the West Laptev Basin, and the other branch departing into grabens that developed to the west of New Siberian Islands forming the Laptev microplate.
Marine and Petroleum Geology, 2001
In northeastern Siberia the active mid-ocean Gakkel Ridge interacts with the continental shelf of the Laptev Sea. Extension has affected the shelf since at least the Early Tertiary and has resulted in the formation of a complex horst and graben system. We present new seismic data from the Laptev Sea including deep seismic soundings. The most prominent rift basin is the Ust' Lena Rift with a minimum E±W width of 300 km at latitude 758N and a Cenozoic in®ll up to 13 km in thickness. The asymmetric shape of the basin and conclusive evidence for a detachment imply a simple-shear geometry. The suggested rift model combines a ramp and¯at geometry for the detachment with ductile stretching beneath the detachment. A major westdipping, hingeline, listric fault separates the Ust' Lena Rift from the Laptev Horst. The 100±150 km wide Laptev Horst is subdivided into three units by narrow rift grabens. Another prominent rift graben is the Anisin Basin, which is located in the northern shelf area. Though the Laptev Sea Rift formed in interaction with an active mid-oceanic ridge, there are indications that the Laptev Sea rift is of thè passive rift' type. The rift was developed east of a SW±NE trending transfer zone which links the Gakkel Ridge to the Laptev Sea Rift.
Laptev Sea Rifted Continental Margin: Modern Knowledge and Unsolved Questions
Polarforschung, 2000
The Laptcv Sea is one of a few unique places where an active oceanic spreaeling axis approaches a continental eelge causing specific structural style dominared by extensive rift structures. In such a place one can stuely the geoclynamics of the initial breakup of the continents that was playing an important role in creating the past anel prescnt-day oceans. The modern unclerstaneling of the Laptcv continental margin geology resulteel from multichannel seismic (MCS) surveys carrieel out since 1986 by Russian anel German rescarch institutions as weil as from scismological observations anel satellite marine gravity elata. These investigations leel to outlining an earlier preelicteel extensive rift systern fonneel at visible continuation of the Gakkel Rielge. However, despite the obvious achievements so me very important questions concerning the geology of this region still remain to be answereel. These are relateel to the structure of the basement of the shelf, geometry of the rift systcm, scisrnic stratigraphy anelage of the rift sedimentary infill. paleogeodynamics anel moelern geoelynamics of the platc bounelary in the Laptev Sea.
The Mesozoic–Cenozoic tectonic evolution of the New Siberian Islands, NE Russia
Geological Magazine, 2014
On the New Siberian Islands the rocks of the east Russian Arctic shelf are exposed and allow an assessment of the structural evolution of the region. Tectonic fabrics provide evidence of three palaeo-shortening directions (NE–SW, WNW–ESE and NNW–SSE to NNE–SSW) and one set of palaeo-extension directions revealed a NE–SW to NNE–SSW direction. The contractional deformation is most likely the expression of the Cretaceous formation of the South Anyui fold–thrust belt. The NE–SW shortening is the most prominent tectonic phase in the study area. The WNW–ESE and NNW–SSE to NNE–SSW-oriented palaeo-shortening directions are also most likely related to fold belt formation; the latter might also have resulted from a bend in the suture zone. The younger Cenozoic NE–SW to NNE–SSW extensional direction is interpreted as a consequence of rifting in the Laptev Sea.
Doklady Earth Sciences, 2001
According to concepts elaborated in the 1970s by researchers from Institute of Geology of the Arctic Regions (NIIGA), the results of aeromagnetic, gravimetric, and geological surveys in the East Siberian Sea (ESS) region suggest that structural elements of the western shelf are represented by basements of different ages along the De Longa Rise and in the Novaya Sibir and Blagoveshchensk sedimentary basins. Fujita and Newberry further proposed that these basins may be underlain by oceanic crust and may represent relics of the Southern Anyui palaeocean. The first multichannel common-depth-point (CDP) seismic reflection profiles in the ESS were acquired by the Laboratory of Regional Geodynamics (LARGE) Geophysical Company in September 1989, using an airgun source of 5.9 I and a 1200-m- long 48-channel seismic streamer. The field data were processed by the GECO Company (Norway). These new data allowed, for the first time, characterize structure and seismostratigraphy of the western ESS shelf. The synonymous sedimentary basin probably originated in the Late Cretaceous on the heterogeneous basement composed of late Mesozoic fold belts extending from the continent and the Hyperborean Massif, which was not affected by the Late Mesozoic dislocations. The basin formation was possibly related to destructive processes that led to the separation of the North American and Eurasian plates in the Arctic. However, extension of the western shelf basement was not significant, and the basin was formed due to a large-scale subsidence initiated at the latest Cretaceous(?).
Geotectonics, 2013
The tectonic evolution of the Arctic Region in the Mesozoic and Cenozoic is considered with allowance for the Paleozoic stage of evolution of the ancient Arctida continent. A new geodynamic model of the evolution of the Arctic is based on the idea of the development of upper mantle convection beneath the continent caused by subduction of the Pacific lithosphere under the Eurasian and North American lithos pheric plates. The structure of the Amerasia and Eurasia basins of the Arctic is shown to have formed progres sively due to destruction of the ancient Arctida continent, a retained fragment of which comprises the struc tural units of the central segment of the Arctic Ocean, including the Lomonosov Ridge, the Alpha-Men deleev Rise, and the Podvodnikov and Makarov basins. The proposed model is considered to be a scientific substantiation of the updated Russian territorial claim to the UN Commission on the determination of the Limits of the Continental Shelf in the Arctic Region.